1. Field of the Invention
The invention relates to railway rolling stock and consists particularly in a radial axle truck with a compatible disc brake system.
2. The Prior Art
In prior two-axle railway trucks in which the axles are steerable to radial positions on curved track, as exemplified in Herbert Scheffel U.S. Pat. No. 4,067,261, particularly FIGS. 17-24 thereof, if substantially non-resilient linkages are used to connect the diagonally opposite axle bearings, the linkages will prevent the axles from moving transversely of the truck with respect to each other sufficiently to accommodate to transverse offsets in the track rails such as occur at turnouts, with the possibility of excessive strains on the bearing adaptors and linkages.
The use of a single disc mounted on the center of a railway axis for gripping engagement by shoes of a disc brake mechanism is exemplified in G. A. Pelikan U.S. Pat. No. 3,314,505, in which the disc brake mechanism is mounted on a transverse beam fixedly supported from the side frames of a truck. If this arrangement were applied to a radial axle truck, upon application of braking forces to the brake mechanism, the tendency of the latter would be to maintain the disc in its normal centered position which would be satisfactory on tangent track but would oppose radiation of the axles on curved track. In another patent to G. A. Pelikan, U.S. Pat. No. 3,344,893, a pair of discs having opposed slightly conical surfaces is mounted at the center of each axle and a wedge-shaped double-faced shoe mounted on a beam carried by the side frames is movable longitudinally toward the axle in the space between the opposed conical disc surfaces so as to brake the respective axle by wedging frictional engagement with the opposed conical surfaces. Because of the force exerted by this shoe device lengthwise of the truck, it too would tend to oppose the action of the wheel generated steering forces to cause radiation of the axles on curved track. B. Pratt U.S. Pat. No. 2,440,020 discloses a brake having three discs mounted in spaced relationship on the middle of each axle, the middle disc being rotatably mounted on the axle and providing a support for a brake mechanism having shoes engageable with the inner surface of the outer discs. The carrier disc and mechanism are provided with an arm extending toward the truck frame or bolster where it is supported by springs. If this arrangement were applied to a radial axle track, the application of unequal forces by the brake shoes to the separate discs on the respective axles would tend to oppose the steering forces on the respective axles and thus interfere with proper radial positioning of the respective axles on curved track.